Photoresists are functional materials crucial to the photolithography processes in large-scale integrated circuit industry. When a photoresist is exposed to ultraviolet radiation, it undergoes a series of chemical reactions, such that after the exposure the dissolution rate thereof in a developing solution is different from that before the exposure. Then, by the processes of developing, film hardening, etching, film removing and so on, specific high precision graphics can be transferred onto the surface of a substrate to be processed.
However, existing diazo-resins cannot be applied in photoresists because the storage periods of the diazo-resins per se and the printed boards made thereby are both short due to the poor thermal stability of the diazo-resins.